1. Field of the Invention
The present invention relates to a programmable wiring for connecting wiring elements in a channel region in a semiconductor integrated circuit for example in a programmable manner.
2. Description of the Prior Art
Among many semiconductor devices there is known one in which wiring elements in a channel region are connected programmable to permit a user to construct a desired logic circuit. Such semiconductor devices sometimes include a switching matrix to connect the wiring elements with each other programmably.
FIG. 5 exemplarily illustrates the construction of such a semiconductor device. As illustrated in FIG. 5, the semiconductor device includes a plurality of function modules 10, in each of which there are incorporated programmable logic circuits, etc. Wiring channel 11 regions are located each extending among the functional modules 10 and wiring elements 12 are laid on the wiring channel 11 longitudinally and laterally. Additionally, a switching matrix 14 is located at longitudinal and lateral intersections of the wiring elements 12.
The switching matrix 14 has a function to connect arbitrary wiring elements 12 in some directions (designated by symbols N, S, E and W in FIG. 5) by turning on and off a program switch in conformity with a program inputted externally, and form a wiring. Ideally, such provision of the programmable switches at intersections of all wirings in the switching matrix 14 can make maximum the flexibility of the connections among the wiring elements.
However, such a programmable switch of the switching matrix typically comprising a large area static random access memory (SRAM) can not be provided at intersections of all wirings, and hence limits the number of those switches, which are possible to be installed. It is therefore needed to install programmable switches in a switching matrix within the above limited number. There is however existent a difficulty thereupon that provided installation positions of those switches are to be arbitrarily determined, unuseable wiring elements would occur when those switches are connected in conformity with programming.